N-substituted thio alkyl phenothiazines

ABSTRACT

This invention describes phenothiazine derivatives which are N-substituted and which contain an additional sulfur molecule in the N substituent.

The present application is a continuation of Ser. No. 07/667,731 filedMar. 11, 1991 now U.S. Pat. No. 5,033,817, which in turn is acontinuation of 07/610,595 filed Nov. 8, 1990, now U.S. Pat. No.5,157,118, which is a continuation of 07/568,105 filed Aug. 16, 1990,now U.S. Pat. No. 5,034,019, which is a continuation of 07/210,609 filedJun. 23, 1988, now abandoned, which is a continuation of 06/908,077filed Sep. 16, 1986 which issued as U.S. Pat. No. 4,785,095 on Nov. 15,1988.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The compositions of the present invention are useful as oxidationinhibitors acting as oxygen-acceptors, peroxide decomposers and electrontransfer agents in anti-oxidant processes.

2. Description of the Art

Phenothiazine compounds are known in lubricant products from the U.S.Pat. No. 2,781,318 issued Feb. 12, 1957 to Cyphers. The alkylphenothiazines of Cyphers are alkylated on the phenylene rings of thephenothiazine structure. Cyphers does not show or suggest the alkylationof the amine nitrogen in phenothiazine. The Cyphers patent is directedto the utility of phenothiazine as an antioxidant and corrosioninhibiting additive for ester, polyester, polyether and other syntheticlubricants.

U.S. Pat. No. 3,536,706 issued Oct. 27, 1970 to Randell suggests thatphenothiazines may be used as additives for synthetic lubricants. Thephenothiazines particularly described by Randell are those containingtertiary alkyl substituents having from 4 to 12 carbon atoms on the arylgroups which make up the phenothiazine structure. Randell also disclosesfused rings on the two phenylene groups which make up the phenothiazinestructure. Stated otherwise, Randell allows the utilization ofnaphthalene for at least one of the two aryl groups in the phenothiazinestructure.

U.S. Pat. 3,803,140 issued to Cook et al on Apr. 9, 1974 describesvarious tertiary alkyl derivatives of phenothiazine. N-alkylsubstitution or N-alkenyl substitution is described on the phenothiazinestructure. Ring alkylation when the phenothiazine is in the freenitrogen form is also shown. Cook et al express a preference for non-Nsubstituted phenothiazine derivatives.

Cook et al also suggest that organic materials which are susceptible tooxidative degradation may benefit through the use of the compounds oftheir invention. Such uses include antioxidants for aliphatichydrocarbons such as gasoline, lubricating oils, lubricating greases,mineral oils, waxes, natural and synthetic polymers such as rubber,vinyl, vinylidene, ethers, esters, amides and urethanes. The compoundsof Cook et al are also suggested for stabilizing aldehydes, andunsaturated fatty acids or esters thereof. Still further utilitiessuggested by Cook et al include the stabilization of organo-metalloidsubstances such as silicone polymers. Another class of uses of thecompounds of Cook et al include the stabilization of vitamins, essentialoils, ketones and ethers.

Normant in U.S. Pat. No. 3,560,531 issued Feb. 2, 1971, describesmetallation of materials having active hydrogens includingphenothiazine. U.S. Pat. No. 3,344,068 issued Sep. 26, 1967, to Waightet al describes antioxidants for ester-based lubricants. Waight et al'scompounds have an N-hydrocarbyl substituted phenothiazine structure. TheN-substituted phenothiazine compounds of Waight et al are alsosubstituted in at least one position on the fused aromatic nuclei. Asecond required component in the compositions of Waight et al is asecondary aromatic amine having two aromatic groups attached to thenitrogen atom.

The preparation of alkylthioalkanols which are useful as intermediatesfor preparing the compounds of the present invention are described inU.S. Pat. No. 4,031,023 to Musser et al. The Musser et al patent wasissued Jun. 21, 1977 and is assigned to The Lubrizol Corporation.

U.S. Pat. No. 2,194,527 to Winthrop et al which issued Nov. 24, 1959,describes pharmaceutical compounds such asomega-(10-phenothiazinyl)alkyl di-alkyl sulfonium salts which are usefulas spasmolytics and in particular antihistaminics. U.S. Pat. No.3,376,224 issued April 2, 1968 to Elliott et al describes phenothiazinederivatives which are stated to be N-substituted methylene compoundswhich contain an ether linkage between the methylene group and an alkylor cycloalkyl radical. According to Elliot et al, the alkyl orcycloalkyl radical may carry an alkoxy or other non-reactivesubstituent.

It has been found in the present invention that the antioxidant activityof a phenothiazine is significantly improved by the presence of asulfur-containing hydrocarbyl moiety as a substituent on thephenothiazine nitrogen atom. The effectiveness is particularly enhancedwhen the sulfur atom of the substituent group is in a beta position(i.e., 2-atoms removed) from the phenothiazine N-atom. Such compounds aslater described herein have excellent anti-oxidant properties inlubricating oils.

Throughout the specification and claims, percentages and ratios are byweight, temperatures are degrees Celsius, and pressures are in Kpascalsgauge unless otherwise indicated. References cited herein areincorporated by reference to the extent that they are applicable.

SUMMARY OF THE INVENTION

The present invention describes phenothiazine derivatives comprisingcompositions of the formula: ##STR1## wherein R¹ is selected from thegroup consisting of higher alkyl, or an alkenyl, aryl, alkaryl andaralkyl and mixtures thereof; R² is alkylene, alkenylene, and aralkyleneand mixtures thereof; R3 and R4 are independently alkyl, alkenyl, aryl,alkaryl, aralkyl, halogen, hydroxyl, alkoxy, and alkylthio, arylthio,fused aromatic rings and mixtures thereof; and a and b are independently0 or greater.

A further embodiment is a product according to formula I and/or III anda major amount of at least one lubricating oil or at least one fuel. Theproduct of formula I may also be formulated at about 1% to 99% by weightwith 1% to 99% by weight of a diluent or solvent

A process is described for preparing the compositions herein describedby

(a) reacting a thio alcohol of the formula

    R.sup.1 SR.sup.2 OH

and,

(b) a phenothiazine derivative of the formula ##STR2## thereby obtainingthe composition of formula I.

Another embodiment of the present invention is the sulfone and sulfoxidederivatives of the aforedescribed compounds wherein R¹ is a hydrocarbylgroup conveniently selected from the group consisting of an alkyl,alkenyl, aryl, alkaryl and aralkyl and mixtures thereof; R² is alkylene,alkenylene, and aralkylene and mixtures thereof; R³ and R⁴ areindependently alkyl, alkenyl, aryl, alkaryl, aralkyl, halogen, hydroxyl,alkoxy, aryloxy, alkylthio, arylthio, fused aromatic rings and mixturesthereof; and a and b are independently 0 or greater. Such compounds maybe represented by the formula ##STR3## where a, b, R¹, R², R³ and R⁴have the values described above. The values of x and y are independently0, 1 or 2 and the sum of x and y is greater than or equal to 1.

DETAILED DESCRIPTION OF THE INVENTION

The first aspect of the invention is obtaining the phenothiazinecompound or phenothiazine derivative utilized to manufacture thecompounds of the present invention. Phenothiazine is itself an articleof commerce and, thus, no further description of this material isrequired.

To obtain the derivatives of phenothiazine useful herein, e.g., where(a) and (b) in formula I are not 0, it is suggested that U.S. Pat.2,781,318 to Cyphers issued Feb. 12, 1957 be consulted. A dialkyldiphenyl amine treated with sulfur at elevated temperatures, such as inthe range of 145° C. to 205° C. for a sufficient time to complete thereaction, gives compounds which may be derivatized within the scope offormula I. Conveniently, a catalyst such as iodine may be utilized toestablish the sulfur bridge. The reaction is essentially clean and doesnot affect the amine hydrogen in the composition. Typically, adialkylated product will be obtained, e.g., where both (a) and (b) areeach 1. The monoalkylated phenothiazine derivatives are convenientlyobtained by utilizing a monoalkylated diphenylamine which is thencyclized to obtain the corresponding monoalkylated phenothiazine.Similarly, phenothiazine may be alkylated with olefins using a Lewisacid catalyst.

While the derivatives R³ and R⁴ have been defined above as alkyl, anyhydrocarbyl group may be employed. It is convenient to utilize alkenyl,aryl, alkaryl, aralkyl, halogen, hydroxyl, alkoxy, alkylthio, arylthioand the like for R³ and R⁴ To obtain the hydroxyl derivative one wouldreact, for example, aniline and hydroquinone to form4-hydroxydiphenylamine which is then cyclized with sulfur. Thecorresponding alkoxy compounds may be obtained by reacting thehydroxy-containing phenothiazine with an alkyl halide.

Similar to obtaining the alkyl derivatives as R³ and R4, the alkenyl,aryl, alkaryl, aralkyl, and fused ring derivatives may be prepared. Thefused ring derivatives may be prepared from phenyl napthylamines whichmay be cyclized by sulfurization to produce benzophenothiazines.Moreover, the corresponding polyaromatic compounds and their alkylderivatives are obtained in a similar fashion. The halogenated forms ofthe product are obtained by treatment of phenothiazine with, forexample, bromine or chlorine. The values for R³ and R⁴ as alkylthio andarylthio are conveniently obtained by treatment of phenothiazine withthiourea and iron chloride. Hydrolysis of the prior obtainedisothiuronium chloride to thiophenol which is then alkylated aspreviously described gives R³ (R⁴) as alkylthio.

Of course, mixtures of the varying values of R³ and R⁴ are includedwithin the scope of the present invention. Thus, R³ may be a chlorogroup, while R⁴ is an alkyl group. The present invention as previouslynoted also allows for R³ and R⁴ to independently be different alkylgroups. That is, R³ and R⁴, while both being alkyl, can be of differentcarbon chain lengths. The position of R³ and R⁴ alkyl groups on thearomatic rings will typically be in the para position to theheterocyclic nitrogen, although para substitution to the heterocyclicsulfur may also occur. It is also convenient to utilize derivativeswhere R³ and R⁴ are independently aryl. Conveniently, R³ and R⁴ ashydrocarbyl moieties will contain from about R³ to about 30 carbon atomsin each moiety. Preferably, R³ and R⁴ as hydrocarbyls will containindependently from about 4 to about 15 carbon atoms.

The second portion of the claimed structure in the present inventionprovides for the definition of R². The value, R² may be an alkylene oralkenylene and conveniently contains in either instance from about 1 toabout 18 carbon atoms. Preferably, R² is a linear alkylene and containsfrom about 2 to about 8 carbon atoms, most preferably 2 carbon atoms,e.g., ethylene. The value of R² may also be satisfied by branched chainor substituted material e.g., typically one in which a methyl group isattached to a short chain alkylene group between the sulfur and thenitrogen. That is, the 1-methyl and 2-methyl ethylene derivatives arecontemplated herein. R² may also be aralkylene such as a phenyl residuependent from an ethylene moiety between the sulfur and the ringnitrogen.

The value of R¹ is conveniently defined as a higher alkyl, or analkenyl, aryl, alkaryl or aralkyl or mixtures thereof. The preferredlinkage for R¹ to the sulfur is primary. To obtain the compounds offormula I, the reaction of R¹ SCH₂ CH₂ OH with phenothiazine isconveniently utilized. A large number of raw materials may be used toprepare the compounds described herein. For example, in the compounds offormula I, R¹ may contain from about 4 to about 50 carbon atoms.Substantial branching may occur in the backbone of the materialsutilized to form the R¹ residue. The residue R¹ is also convenientlyobtained containing from about 6 to about 20 carbon atoms in formula I.Where the sulfones and sulfoxides are obtained from the compounds offormula I, the value of R¹ is conveniently from about 1 to about 50carbon atoms, preferably from about 4 to about 50 carbon atoms, mostpreferably from about 6 to about 20 carbon atoms.

A suggested species for R¹ herein is: ##STR4## which is derived from thereaction of thiodiethanol and phenothiazine.

It is desirable that an oleophilic group be present in the productpendant from the nitrogen atom in the phenothiazine to ensure oilsolubility or dispersability. Ordinarily, the oleophilic group issupplied by R¹. Alternatively, the values of R³ and R⁴ may be adjustedto increase the oleophilic nature of the product and to minimize theneed for an oleophilic chain corresponding to R¹ in the molecule. It isalso highly desirable for inhibitor performance that the pendant sulfurbe in the beta position to the nitrogen in the phenothiazine structure.

It is to be understood that the values R¹, R², R³ and R⁴ may containadditional hetero atoms or hetero groups including such moieties asamine, sulfides, phenols, ether linkages, amides, carboxyls and thelike. Such groups, as long as they allow functioning of the desiredanti-oxidant properties may be included at any level within the variousR¹ -R⁴ groups, preferably at not greater than 20% by weight of therespective group.

The sulfones and the sulfoxides of the phenothiazine derivatives(formula I) may be obtained by partially or fully oxidizing the sulfuratoms within the molecule. In Formula I, both sulfur atoms aresusceptible to oxidation to sulfoxide and sulfones so that both mayparticipate in the anti-oxidant process. Both of the sulfur atomsundergo oxidation to the sulfoxide simultaneously. It then depends onthe relative activity of the sulfoxide groups as to whether the ringsulfoxide is then changed to a sulfone or whether the side chainsulfoxide is oxidized to the sulfone. The sulfone formation is dependentupon the sulfoxide formation and, thus, mixtures of the sulfones and thesulfoxides are often obtained. The benefit of the sulfone and sulfoxidederivatives is that they provide additional anti-oxidant properties. Thesulfone is a useful compound in that it may undergo further oxidationthus prolonging the protection of the lubricant against degradation.

A convenient mixture of the compound of formula I and the sulfones andsulfoxides is typically obtained in a ratio of from about 1: 0.1: 0.1 toabout 0.5: 1:1.

The types of lubricating oils which may be utilized herein are describedas being of a lubricating viscosity and may be based on natural oils,synthetic oils, or mixtures thereof. The lubricating oils are also apreferred diluent for use herein.

Natural oils include animal oils and vegetable oils (e.g., castor oil,lard oil) as well as mineral lubricating oils such as liquid petroleumoils and solvent-treated or acid-treated mineral lubricating oils of theparaffinic, naphthenic or mixed paraffinicnaphthenic types. Oils oflubricating viscosity derived from coal or shale are also useful.Synthetic lubricating oils include hydrocarbon oils and halosubstitutedhydrocarbon oils such as polymerized and interpolymerized olefins (e.g.,polybutylenes, polypropylenes, propyleneisobutylene copolymers,chlorinated polybutylenes, etc.); poly(1-hexenes), poly(1-octenes),poly(1-decenes), etc. and mixtures thereof; alkylbenzenes (e.g.,dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes,di-(2-ethylhexyl)-benzenes, etc.); polyphenyls (e.g., biphenyls,terphenyls, alkylated diphenyl ethers and alkylated diphenyl sulfidesand the derivatives, analogs and homologs thereof and the like.

Alkylene oxide polymers and interpolymers and derivatives thereof wherethe terminal hydroxyl groups have been modified by esterification,etherification, etc., constitute another class of known syntheticlubricating oils that can be used. These are exemplified by the oilsprepared through polymerization of ethylene oxide or propylene oxide,the alkyl and aryl ethers of these polyoxyalkylene polymers (e.g.,methylpolyisopropylene glycol ether having an average molecular weightof about 1000, diphenyl ether of polyethylene glycol having a molecularweight of about 500-1000, diethyl ether of polypropylene glycol having amolecular weight of about 1000-1500, etc.) or mono- and polycarboxylicesters thereof, for example, the acetic acid esters, mixed C₃ -C₈ fattyacid esters, or the C₁₃ OXO acid diester of tetraethylene glycol.

Another suitable class of synthetic lubricating oils that can be usedcomprises the esters of dicarboxylic acids (e.g., phthalic acid,succinic acid, alkyl succinic acids, alkenyl succinic acids, maleicacid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipicacid, linoleic acid dimer, malonic acid, alkyl malonic acids, alkenylmalonic acids, etc.) with a variety of alcohols (e.g., butyl alcohol,hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol,diethylene glycol monoether, propylene glycol, etc.) specific examplesof these esters include dibutyl adipate, di(2-ethylhexyl) sebacate,di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecylazelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the2-ethylhexyl diester of linoleic acid dimer, and the complex esterformed by reacting one mole of sebacic acid with two moles oftetraethylene glycol and two moles of 2-ethylhexanoic acid and the like.

Esters useful as synthetic oils also include those made from C₅ to C₁₂monocarboxylic acids and polyols and polyol ethers such as neopentylglycol, trimethylol propane, pentaerythritol, dipentaerythritol,tripentaerythritol, etc.

Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy-, orpolyaryloxy-siloxane oils and silicate oils comprise another usefulclass of synthetic lubricants (e.g., tetraethyl silicate, tetraisopropylsilicate, tetra-(2-ethylhexyl)silicate, tetra-(4-methyl-hexyl)-silicate,tetra-(p-tert-butyl-phenyl)silicate,hexyl-(4-methyl-2-pentoxy)disiloxane, poly(methyl)siloxans,poly(methylphenyl)siloxanes, etc.). Other synthetic lubricating oilsinclude liquid esters of phosphorus-containing acids (e.g., tricresylphosphate, trioxtyl phosphate, diethyl ester of decane phosphonic acid,etc.), polymeric tetrahydrofurans and the like.

Unrefined, refined and rerefined oils, either natural or synthetic (aswell as mixtures of two or more of any of these) of the type disclosedhereinabove can be used in the concentrates of the present invention.Unrefined oils are those obtained directly from a natural or syntheticsource without further purification treatment. For example, a shale oilobtained directly from retorting operations, a petroleum oil obtaineddirectly from primary distillation or ester oil obtained directly froman esterification process and used without further treatment would be anunrefined oil.

Refined oils are similar to the unrefined oils except they have beenfurther treated in one or more purification steps to improve one or moreproperties. Many such purification techniques are known to those skilledin the art such as solvent extraction, secondary distillation,hydrotreating, hydrocracking, acid or base extraction, filtration,percolation, etc.

Rerefined oils are obtained by processes similar to those used to obtainrefined oils applied to refined oils which have been already used inservice. Such rerefined oils are also known as reclaimed or reprocessedoils and often are additionally processed by techniques directed toremoval of spent additives and oil breakdown products. Most preferably,the oil used herein is a petroleum derived oil.

The fuels which may be treated with the composition of this inventioninclude both solid and normally liquid fuels. That is, the antioxidanteffect of the fuels prevents the fuel from degrading prior to thecombustion process. By eliminating or minimizing oxidation of the fuel,the fuel value (caloric content) of the fuel remains higher. It may alsobe observed under certain situations that the fuel by being more stableis less prone to spontaneous combustion. Among the solid fuels which maybe utilized are coal, shale, peat, wood, organic refuse, charcoal andthe like. Liquid fuels encompass the lighter petroleum fractions such asgasoline, kerosene, and the like as well as other fractions such asmiddle distillate fuel oils. Typical middle distillate fuel oils whichmay be treated with the compositions of this invention include Number1,2 and 4 oils as defined by ANSI/ASTM Standard D-396-79 and other suchmaterials. Combinations of such fuel oils with straight run, vacuum run,and other specially treated residual oils can also be advantageouslytreated with the compositions of the present invention.

The lubricants and fuels of the present invention may include all matterof typically included ingredients such as dyes, adjuvants, dispersants,other antioxidants, overbased materials and the like. Fuels may alsoinclude cetane improvers and octane enhancers. Greases may also benefitfrom the anti-oxidants described herein.

A further description of the process by which the compounds herein maybe formed is as follows.

The phenothiazine and its various derivatives are converted to thecompounds of formula I by contacting the phenothiazine compound offormula II with the desired thio alcohol of the formula R¹ SCH₂ CH₂ OH.The thio alcohol may be obtained by the reaction of the mercaptan, R¹ SHwith ethylene oxide under basic conditions. Alternatively, the thioalcohol is obtained by reacting the corresponding terminal olefin withmercaptoethanol under free radical conditions such as by using, forexample, 2,2'-azobis (isobutyronitrile) as an initiator.

The reaction conditions for obtaining the formula I compounds includethe use of an inert solvent such as toluene, benzene, and the like. Astrong acid catalyst such as sulfuric acid or para-toluene sulfonic acidat about 1 part to 50 parts per 1000 parts of the phenothiazine issuggested. The reaction is conducted under an inert gas blanket. Thetemperature conditions are conveniently set at the reflux temperaturewith removal of the water as it is formed. Conveniently, the reactiontemperature is maintained between 80° C. and 170° C.

The amount of the diluent or solvent utilized herein to prepare aconcentrate is typically that amount needed to solubilize or dispersethe compound of Formula I. Typically, the diluent or solvent is presentat about 1% to 99% by weight, conveniently at about 60% to 99% by weightof the composition. The phenothiazine derivatives described herein areuseful at about 0.1% to 10% by weight in a fully formulated product.Suggested diluents and solvents are those lubricants and fuels in whichthe compounds of formula I will eventually be added. Any other diluentor solvent may be used provided that such does not interferesubstantially with the function of the end product. Oxidation of thecompounds of formula I to the sulfone and sulfoxide occurs naturallyunder crankcase conditions. If the sulfone and sulfoxide are desired asdiscrete compounds, they may be obtained by using an oxidant such ashydrogen peroxide. The compounds of formula I are converted to thesulfone or sulfoxide in a solvent such as glacial acetic acid or ethanolunder an inert gas blanket. The partial oxidation takes placeconveniently at about 20° to 150° C. The degree of sulfone and sulfoxideformation is determined by practice.

Oxidation of lubricants occur due to heat and shear action on thelubricating oil in the presence of oxygen and other oxidants. In theabsence of antioxidants, the lubricating oil will build up viscosity,deposits will form on engine parts, and corrosive acids form, all ofwhich are detrimental to engine performance and life. The use ofantioxidants such as the type described herein are particularly helpfulin reducing carbon radicals, carbon peroxy radicals, and or peroxideswhich are formed in the lubricating product.

The following are examples of the present invention.

EXAMPLE I

One mole of phenothiazine is placed in a one liter, round bottom flaskwith 300 ml of toluene. The reactants are maintained under a nitrogenblanket. To the mixture of phenothiazine and toluene is added 0.05 moleof sulfuric acid catalyst. The mixture is then heated to refluxtemperature and 1.1 moles of n-dodecylthioethanol is added dropwise overa period of approximately 90 minutes. Water is continuously removed asit is formed in the reaction process.

The reaction mixture is continuously stirred under reflux untilsubstantially no further water is evolved. The reaction mixture is thenallowed to cool to 90° C. The sulfuric acid catalyst is neutralized withsodium hydroxide. The solvent is then removed under a vacuum of 2KPa at110° C. The residue is filtered giving a 95% yield of the desiredproduct. The product has a purity of greater than 90% of the desiredcompound.

The compound is identified as having the value of R¹ as C₁₂, R² beingethylene, and both a and b are zero (e.g., the aromatic rings of thephenothiazine contain only hydrogen substitution).

EXAMPLE II

One mole of phenothiazine is placed in a one liter, round bottom flaskwith 300 ml of toluene. The reactants are maintained under a nitrogenblanket. To the mixture of the phenothiazine and toluene is added 0.05mole of sulfuric acid as a catalyst. The mixture is then heated toreflux temperature and 1.1 moles of n-hexylthioethanol is added dropwiseover a period of approximately 90 minutes. Water is continuously removedas it is formed in the reaction process.

The reaction mixture is continuously stirred under reflux untilsubstantially no more water is evolved. The reaction mixture is thenallowed to cool to 90° C. The sulfuric acid catalyst is neutralized withsodium hydroxide. The solvent is then removed under a vacuum of 2KPa at110° C. The residue is filtered giving a 95% yield of the desiredproduct. The product has a purity of greater than 90% of the desiredcompound.

The compound is identified as having the value of R¹ as C₆, R² beingethylene, and both a and b are zero. A similar result will be obtainedwhen using n-octylthioethanol.

EXAMPLE III

Phenothiazine is alkylated with nonene, using aluminum chloride as aFriedel Crafts catalyst under conventional conditions. One mole of thedialkylated phenothiazine is placed in a one liter round bottom flaskwith 300 milliters of toluene. A nitrogen sparge and blanket areemployed. To the mixture of the dialkylated phenothiazine and toluene isadded 0.05 mole of sulfuric acid as a catalyst. The mixture is thenheated to reflux and 1.1 moles of n-dodecylthioethanol is added dropwiseover a period of approximately 90 minutes. Water is continuously removedas it is formed.

The reaction mixture is continually stirred under reflux untilsubstantially no further water is obtained. The reaction mixture is thenallowed to cool to 90° C. The sulfuric acid catalyst is neutralized withsodium hydroxide. The solvent is then removed under a vacuum of 2KPa at110° C. The residue is then filtered giving a 95% yield of the desiredproduct. The product has a purity of greater than 80% of the desiredcompound.

The compound is identified as having the value of R¹ being C₁₂, and R³and R⁴ being in the para position as C₉, R² is ethylene and a and b areeach one.

A modification of this example is to use dodecyl mercaptan which ispre-reacted with styrene oxide under basic conditions. The substitutionof this reactant above gives R² as a ethylene group substituted with apendent phenyl group.

EXAMPLE IV

One mole of phenyl alpha-naphthylamine is placed in a one liter roundbottom flask. A nitrogen sparge is applied to flush air from thereaction vessel. The reactants are maintained under the nitrogenblanket. The amine is first sulfurized at 190° C. with an iodinecatalyst under conventional conditions. Then, 1.1 moles of n-stearylthioethanol is utilized to alkylate the sulfurized product in 300 mltoluene using a small amount of sulfuric acid catalyst. The reaction isallowed to proceed over a period of 90 minutes. Water is continuouslyremoved as it is formed in the reaction process. The reaction mixture iscontinually stirred at reflux until substantially no more water isevolved. The reaction mixture is then allowed to cool to 90° C. Thesulfuric acid catalyst is then neutralized with sodium hydroxide. Thesolvent is then removed under a vacuum of 2KPa at 110° C. to give thebenzophenothiazine product.

EXAMPLE V

One mole of phenothiazine is placed in a one liter, round bottom flaskwith 300 ml of toluene. The reaction is maintained under a nitrogenblanket. To the mixture of the phenothiazine and toluene is added 0.05mole of sulfuric acid as a catalyst. The mixture is then heated toreflux temperature and 1.1 moles of phenylthioethanol is added dropwiseover a period of approximately 90 minutes. The phenylthiothethanol isobtained from the reaction of thiophenol and ethylene oxide with a basiccatalyst. Water is continuously removed as it is formed in the reactionprocess.

The reaction mixture is continuously stirred under reflux untilsubstantially no further water is evolved. The reaction mixture is thenallowed to cool to 90° C. The sulfuric acid catalyst is neutralized withsodium hydroxide. The solvent is then removed under a vacuum of 2KPa at110° C. The residue is filtered giving a 95% yield of the desiredproduct. The product has a purity of greater than 90% of the desiredcompounds.

The compound of this example is identified as having R¹ as phenyl, R²being ethylene, and both a and b are zero. (e.g., the aromatic ringscontain only hydrogen substitutions).

EXAMPLE VI

Two moles of the dialkylated phenothiazine of Example III are placed ina two liter, round bottom flask with 600 ml of toluene. The reaction ismaintained under a nitrogen blanket. To the mixture of the alkylatedphenothiazine derivative and toluene is added 0.1 mole of sulfuric acidas a catalyst. The mixture is then heated to reflux temperature and 1.1moles of thiodiethanol is added dropwise over a period of approximately90 minutes. Water is continuously removed as it is formed in thereaction process.

The reaction mixture is continuously stirred under reflux untilsubstantially no more water is evolved. The reaction mixture is thenallowed to cool to 90° C. The sulfuric acid catalyst is neutralized withsodium hydroxide. The solvent is then removed under a vacuum of 2KPa at110° C. The residue is filtered giving a 95% yield of the desiredproduct. The product has a purity of greater than 80% of the desiredcompound.

The compound obtained is identified as having a symmetricalbis-phenothiazine structure, R² is ethylene, a and b are each 1 with R³and R⁴ being nonyl. This product is generally described as: ##STR5##

EXAMPLE VII

The oxidized product of Example I is obtained by placing 0.2 mole of theproduct therein in a one liter round bottom flask. Ethanol in the amountof 400 ml is then added, followed by a nitrogen sparge. An inert gasblanket is thereafter retained during the reaction. The reaction is thenheated to reflux and 30% hydrogen peroxide (0.2 mole) is added dropwiseover one-half hour. The reaction is stirred under reflux for 5 hours.

The product is then allowed to cool and water in the amount of 400 ml ismixed with the product. The lower organic layer is separated, dried withmagnesium sulfate, and the residual solvent removed at 100° C. at 2Kpa.The corresponding oxidized product of Example I is thus obtained.

EXAMPLE VIII

A series of lubricant products are prepared by mixing an SAE 30 motoroil in the amount of 1000 parts with 50 parts each of the products ofExample I-VII. The resultant products show desirable antioxidantactivity and lubricant activity. Mixtures of products I and VII in equalamounts are desirable in this example.

EXAMPLE IX

Number 2 diesel fuel in the amount of 1000 parts is treated with 50parts of each of the products of Examples I-VII to give a fuel which isresistant to storage temperature oxidation.

EXAMPLE X

A series of blends are made for lubricant top treatments ofphenothiazine derivatives. The base oil used is 10W30 motor oil. Theblends are tested for oxidation stability using Pressure DifferentialScanning Calorimetry. Time is measured in minutes to the exotherm peakmaximum. All phenothiazine products have a R₂ =C₂ H₄, a=0, b=0, and areemployed at equal sulfur level.

    ______________________________________                                                             TREATMENT                                                TEST     R.sub.1 =   LEVEL %     TIME                                         ______________________________________                                        1        n-C.sub.6 H.sub.13                                                                        0.40        42                                           2        n-C.sub.8 H.sub.17                                                                        0.43        48                                           3        n-C.sub.12 H.sub.25                                                                       0.50        35                                            4*      n-C.sub.12 H.sub.25                                                                       0.50        48                                            5*      n-C.sub.12 H.sub.25                                                                       0.50        51                                           6        No Additive 0           less than 15                                 7        IIID Engine Test borderline                                                                       26                                                        fail for a fully formulated                                                   package                                                              ______________________________________                                         *Products 4 and 5 are prepared according to Example VII by using H.sub.2      O.sub.2 at 1 mole and 2 moles per mole of the phenothiazine derivative,       respectively.                                                            

*Products 4 and 5 are prepared according to Example VII by using H₂ O₂at 1 mole and 2 moles per mole of the phenothiazine derivative,respectively.

The test results show the products of the invention exceed the minimumrequirements for a IIID engine test pass.

EXAMPLE XI

A series of blends are made using Union West 90N oil. In these fullyformulated blends, the phenothiazine compounds replaced the sulfur andnitrogen oxidation inhibitors normally present in an automatictransmission fluid.

These blends are tested for air oxidation measuring hours to failure.

All the phenothiazine compounds in the table have R₂ =C₂ H₄, a=0, b=0,and are employed at equal sulfur level.

    ______________________________________                                                           TREATMENT   HOURS TO                                       TEST  R.sub.1 =    LEVEL %     FAILURE                                        ______________________________________                                        1     n-hexyl      0.38        105                                            2     n-octyl      0.41        105                                            3     n-dodecyl    0.52        105                                            ______________________________________                                    

The fully formulated products of the invention are equivalent inperfomance to a conventional automatic transmission fluid which uses a0.6% conventional oxidation inhibitor package.

What is claimed is:
 1. A composition comprising a major amount of an oilof lubricating viscosity, and sulfone of: ##STR6## wherein R¹ isselected from the group consisting of higher alkyl, or an alkenyl, arylphenothiazine derivatives, alkaryl and aralkyl and mixtures thereof; R²is alkylene, alkenylene, and aralkylene and mixtures thereof; R³ and R⁴are independently alkyl, alkenyl, aryl, alkaryl, aralkyl, halogen,hydroxyl, alkoxy, alkylthio, arylthio, fused aromatic rings and mixturethereof; and a and b are independently 0 or greater.
 2. The compositionof claim 1 wherein R¹ is alkyl.
 3. The composition of claim 2 wherein R¹contains at least 4 carbon atoms.
 4. The composition of claim 3 whereinR¹ contains from about 4 to about 50 carbon atoms.
 5. The composition ofclaim 1 wherein R² is a linear alkylene.
 6. The composition of claim 1wherein R³ and R⁴ are independently alkyl.
 7. The composition of claim 6wherein R³ and R⁴ independently contain from about 3 to about 30 carbonatoms.
 8. The composition of claim 1 wherein R³ is hydroxyl.
 9. Thecomposition of claim 1 wherein R² is ethylene.
 10. The composition ofclaim 1 wherein R¹ is an alkyl containing about 6 to about 20 carbonatoms, R² is ethylene, and a and b are each
 0. 11. The composition ofclaim 1 wherein R¹ is ##STR7##
 12. A composition according to claim 1further comprising a fuel.
 13. A composition according to claim 1further comprising a grease.